so today i replaced the stock spark plugs at 61000 with new stock ones from the dealer they are the ngk ones for the byp engine. i did not replace the coils.
so after install the car turned over fine and ideled normally but after reving the engine "after it was up to temp" the rpms would drop below the normal 850 to 800 range to around 600 then it would bounce back up. also in second gear the car has a significant loss of power in the low end and the spin up time feels slow. and at one point durning the test drive it shut off at a light but cranked on fine and that hasnt happened since. any ideas???